Deteriorative Reactions in Foods During Storage

Transcription

1 Deteriorative Reactions in Foods During Storage M. Nurcholis STP. MP Food Packaging and Shelf Life (2012)

2 OVERVIEW Introduction Deteriorative Reaction in Foods Rates of Deteriorative Reactions (RDR) Extrinsic Factors to control RDR Conclusion

3 Introduction Principle : Provide a brief overview of the major biochemical, chemical, physical, biological changes that occur in foods during processing & storage. How these combine to affect food quality.

4 Introduction Knowledge of such changes is essential before a sensible choice of packaging materials can be made. The rate of such changes can be minimized by selection of the correct packaging materials. How about the classification of Undesirable changes that occur in foods

5 Classification of Undesirable Changes that occur in foods Loss of solubility Loss of WHC Toughening Softening Rancidity Other off flavors Darkening Bleaching Off colors Texture Flavor Color Increase / decrease praticle size Non uniformity Appearance Loss of Vitamins, Minerals, Proteins, Lipids Nutritive value

6 OVERVIEW Introduction Deteriorative Reaction in Foods Rates of Deteriorative Reactions (RDR) Extrinsic Factors to control RDR Conclusion

7 Deteriorative Reaction in Foods 1. Enzymatic changes Enzymes can act as : Catalyst : accelerating the rate of chemical reaction. Specificity : enabling the food processor to selectively modify individual food components. Regulatory : controlling biochemcial processes.

8 Deteriorative Reaction in Foods 1. Enzymatic changes Type : Exogenous enzymes : microbial enzymes during food spoilage changes sensory quality of foods. Endogenous enzymes : o Autolysis in fish postharvest o Glycolysis in postmortem o Senescence & spoilage of fruits & Vegetables o Lipid and phenolic oxidation

9 Deteriorative Reaction in Foods 1. Enzymatic changes Type : Lipase & lipoxygenase in milk lipid oxidation affectting the color, flavor, texture. Lactase in milk : formation of lactic acid curd, sour taste Phenolase leading to browning Phospholipase leading to changes in texture

10 Deteriorative Reaction in Foods 1. Enzymatic changes How to control enzymatic changes? Temperature ph Aw Chemical substances which inhibit enzymes Alteration of substrate Alteration of products Preprocessing control

11 Deteriorative Reaction in Foods 2. Chemical Changes Sensory Quality : 1. Lipid oxidation 2. Nonenzymic brwoning 3. Color changes (Chlorophylls, Heme pigments, anthocyanins, carotenoid, natural pigment) 4. Flavor changes Nutritional Quality : Vitamins, proteins, lipids

12 Deteriorative Reaction in Foods 2. Chemical Changes The rates of these chemical reactions are dependent on a variety of factors amenable to control by packaging including : light, oxygen concentration, temperature, Aw. The packaging also play a major role in controlling these factors.

13 Deteriorative Reaction in Foods 2. Chemical Changes Chemical reaction that can lead to deterioration of food quality or impairment of safety : 1. Non enzymic browning 2. Lipid hydrolysis & oxidation 3. Protein denaturation & cross linking 4. Oligo & polysaccharide hydrolysis 5. Protein hydrolysis 6. Polysaccharide synthesis 7. Degradation of specific natural pigments 8. Glycolytic changes

14 Deteriorative Reaction in Foods 2. Chemical Changes (Sensory Quality) a. Lipid Oxidation (Autooxidation) : The reaction of molecular oxygen by a free radical mechanism with hydrocarbons and other compounds. The reaction of free radical is extremely rapid. Lipid which contain multiple double-bonded systems (ex : PUFA, phospholipids) are susceptible to autooxidation. The mechanism of lipid oxidation (4 steps) : initiation, propagation, branching and terminataion.

15 Deteriorative Reaction in Foods 2. Chemical Changes (Sensory Quality) a. Lipid Oxidation (Autooxidation) : Initiation : takes place by loss of hydrogen radical due to heat, light or trace metals. Propagation : lipid-free radical reacts with O2 peroxy free radicals, then react with more lipid hydro-peroxides. Branching process : increase in free radicals from decomposition of hydroperoxides. Termination : elimintion of free radicals by addition of two free radicals stable radical / unreactive.

16 Deteriorative Reaction in Foods 2. Chemical Changes (Sensory Quality) b. Nonenzymic browning : One of the major deteriorative chemical reactions which occurs during storage of dried & concentrated foods. Maillad ractions (3 stages) : 1. Early Maillard chemically well-defined steps w/o browning 2. Advanced Maillard lead the formation of volatile or soluble substances 3. Final Maillard leading to insoluble polymers

17 Deteriorative Reaction in Foods 2. Chemical Changes (Sensory Quality) b. Nonenzymic browning : The initial reaction involves a simple condensation between an aldehyde (usually reducing sugar) and an amine (usually protein or amino acids) to give a glycosylamine via Schiff s base The glycosylamine then undergoes an amadori and various flavor compound. Strecker degradation involves oxidative degradation of amino acids

18 Deteriorative Reaction in Foods 2. Chemical Changes (Sensory Quality) b. Nonenzymic browning : Transamination of the Schiff base, substitution of amino-deoxy-ketose Formation of heterocyclic compounds such as pyrazines and pyrroles (brown melanoidin pigments)

19 Deteriorative Reaction in Foods 2. Chemical Changes (Sensory Quality) c. Color Changes : Acceptability of color in a given food is influenced by many diverse factors, including cultural, geographical, and sociological aspects of the population The Nature changes of pigments : 1. Chlorophylls 2. Heme Pigments 3. Anthocyanins 4. Carotenoids

20 2. Chemical Changes Color changes 1. Chlorophylls Heat & Acid Pheophytinization Dark color (brown) Ex : photooxidation of green peas & beans packed in clear glass containers loss of desirable color. 2. Heme Pigments Oxygen + myoglobin oxymyoglobin or brown metmyoglobin Ex : loss of desirable color in fresh meat.

21 2. Chemical Changes Color Changes 3. Anthocyanins water soluble pigments in plants composed of an aglycone (anthocyanidin) esterified to one or more of five sugars (glucose, rhamnose, xylose, galactose, arabinose) Decolorization of the pigments is depend on ph. Stabile in low ph Neutral ph (no color), acid ph (red-purple), basic ph (light blue)

22 2. Chemical Changes Color Changes 4. Carotenoids : Lipid soluble Yellow and red colors of plant and animal products Include a class of hydrocarbons called carotenes & their oxygenated derivatives called xantophylls. Autooxidize by oxygen, light, heat and prooxidants

23 2. Chemical Changes Flavor Changes Lipids Oxidation Aldehydes, ketones (off-flavor) O 2, light, ph, heat The volatile flavors autooxidation cause : painty, fatty, metallic flavors

24 2. Chemical Changes 2. Nutritional Changes a. Vitamin Vitamin C destruction ph, metal, oxygen

25 General Stability of Vitamins to Environmental Effects Nutrient Oxygen Light Temperature Vitamin A U U U Vitamin B6 S U U Vitamin B12 U U S Biotin S S U Vitamin C U U U Carotenes U U U Vitamin D U U U Vitamin K S U S Tocopherols U U U Source : Robertson (1993)

26 2. Chemical Changes b. Protein Protein degradation - Oxidation - Protein + lipid - Maillard reaction c. Lipids Lipids degradation Peroxide Oxygen

27 2. Chemical Changes Maillard Reaction Reducing sugars & Amine off color brown color (melanoidin pigment) Rasemination in amino acids Changes amino acid configuration : L-amino acid D-amino acid Loss of nutritional properties, primarily from losses in the amino acid lysine.

28 Deteriorative Reaction in Foods 3. Physical Changes Geometrical Thermal Optical Mechanical Rheological Electrical Hydrodynamic

29 3. Physical Changes Characteristics : Defect on packaging Over heat sealing Nicked packaging Microbial growth product is unsafety Off Smell, taste, and flavor Density changes Viscosity changes

30 Deteriorative Reaction in Foods 3. Physical Changes Geometrical Include : size, shape, volume, density, surface area Related to : homogenous food units, texture characteristics Texture can be divided into 2 classes : 1. Particle size & shape : gritty, grainy 2. Particle size & orientation : fibrous, cellular Ex of physical changes : Hygroscopic, Caking, agglomeration in food powders (starchy powders, proteinaceous, crystalline sugar, amorphous sugar, fatty)

31 Deteriorative Reaction in Foods 3. Physical Changes Powders Type Starchy powders (wheat flour) Proteinaceous (soy isolate) Crystalline sugar (sucrose) Amorphous sugar(dehydrated fruit juices) Fatty (soup mix) How to control physial changes (caking)?? Using antcaking agents, control Aw

32 Deteriorative Reaction in Foods 4. Biological Changes Microorganisms 1. Bacteria 2. Fungi 3. Yeast Macroorganisms 1. Insect 2. Rodentia

33 4. Biological Changes A. Microorganisms : Acid formation decrease ph Protein denaturation floculation Slime formation Viscosity changes Lipolysis H2S, amoniak, amine, indole formation

34 Deteriorative Reaction in Foods 4. Biological Changes How to Control Microorganisms growth??? a.intrinsic Factors * ph * Aw * Nutrient * Eh * Antimicrobial substances * Biological structures

35 4. Biological Changes b. Extrinsic Factors * Temperature Most pathogens are mesopihilic * RH influence Aw of food * Gas concentration MAP (Modified Atmosphere Packaging) preventing the growth of aerobic m.o

36 4. Biological Changes c. Packaging materials Microorganisms (mold, yeast, bacteria) cannot penetrate material of plastic film and metal foils Heat resistant plastic/aluminium foil microbial growth test

37 4. Biological Changes Approximate Minimum Aw Values for The Growth of Microorganisms in Foods Most spoilage bacteria Most spoilage yeasts Most spoilage molds 0,91 0,88 0,80 Halophilic bacteria Xerophilic bacteria Osmophilic yeast 0,75 0,65 0,60

38 4. Biological Changes B. Macroorganisms a. Insects Temp growth : C Water content > 11% Product : cereal, milk and its derivates,fruits,dried meat b. Rodentia : Mouse Control sanitation

39 4. Biological Changes Resistance of Materials to Insect Penetration Type Excellent Good Fair Poor Polycarbonate, Polyethylene terepthalate Celluose acetate, polyamide, PE (0,254 mm), PP, PVC (unplasticized) Acrylonitrile, PE (0,12 mm) Kraft paper, paper, PE (0,025-0,1 mm)

40 4. Biological Changes Methods for Obtaining Insect Resistance of Packaging Materials Select a film thickness Use a film adhesive containing approved insecticide Add an insecticide directly to the packaging material Use shrink film overwraps Seal carton flaps completely

41 OVERVIEW Introduction Deteriorative Reaction in Foods Rates of Deteriorative Reactions (RDR) Extrinsic Factors to control RDR Conclusion

42 Rates of Deteriorative Reactions Zero order reactions First order reactions Microbial Growth and Destruction

43 OVERVIEW Introduction Deteriorative Reaction in Foods Rates of Deteriorative Reactions (RDR) Extrinsic Factors to control RDR Conclusion

44 Extrinsic Factors Controlling RDR We should control temperature, Aw, Gas Atmosphere and light to protect agricultural and food products. Effect of Temperature Effect of Aw Effect of Gas Atmosphere Effect of Light

45 OVERVIEW Introduction Deteriorative Reaction in Foods Rates of Deteriorative Reactions (RDR) Extrinsic Factors to control RDR Conclusion

46 Th an nk You